State and federal laws regulate the discharge of oxides of nitrogen, such as nitrogen monoxide and nitrogen dioxide (collectively referred to herein as NOx), to the atmosphere. Therefore, in processing facilities in which NOx is present in the process exhaust streams, these streams must be treated prior to release into the environment. An example of such a facility is a semiconductor processing facility, and especially a facility involved in the processing of silicon wafers. Some of these process exhaust streams result from the use of nitric acid, such as in etching and cleaning processes, however, the present invention is applicable to treating any process stream containing NOx, regardless of the original source of the NOx.
A variety of treatment mechanisms have been developed to remove NOx from process exhaust streams. For example, one known process is discussed in U.S. Pat. No. 5,637,282, the disclosure of which is hereby incorporated by reference. That system involves removing NOx from a process exhaust stream through scrubbing with an aqueous peroxide solution. While effective, this system requires the processing facility be equipped with suitable handling and storage equipment for hydrogen peroxide. It also requires a considerable flowrate of once-through water, which must be disposed of after use.